/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.beanutils.expression;

/**
 * Property Name Expression Resolver.
 * <p>
 * Methods such as PropertyUtilsBean's <code>setNestedProperty()</code> method use a <code>Resolver</code> to process a <i>property name</i>
 * expression and resolve <i>nested</i>, <i>indexed</i> and <i>mapped</i> property names. The following code provides an example usage demonstrating
 * all the methods:
 * 
 * <pre>
 * // Iterate through a nested property expression
 * while (resolver.hasNested(name)) {
 * 
 *     // isolate a single property from a nested expresion
 *     String next = resolver.next(name);
 * 
 *     // Process...
 *     String property = resolver.getProperty(next);
 *     if (resolver.isIndexed(next)) {
 * 
 *         int index = resolver.getIndex(next);
 *         bean = getIndexedProperty(bean, property, index);
 * 
 *     } else if (resolver.isMapped(next)) {
 * 
 *         String key = resolver.getKey(next);
 *         bean = getMappedProperty(bean, property, key);
 * 
 *     } else {
 * 
 *         bean = getSimpleProperty(bean, property);
 * 
 *     }
 * 
 *     // remove the processed property from the expression
 *     name = resolver.remove(name);
 * }
 * </pre>
 * 
 * In order to create an implementation, it is important to understand how BeanUtils/PropertyUtils uses the <code>resolver</code>. The following are
 * the main methods that use it:
 * <ul>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean}</li>
 * <ul>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#getIndexedProperty(Object, String)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#getMappedProperty(Object, String)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#getNestedProperty(Object, String)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#getPropertyDescriptor(Object, String)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#getSimpleProperty(Object, String)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#setIndexedProperty(Object, String, Object)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#setMappedProperty(Object, String, Object)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#setNestedProperty(Object, String, Object)}</li>
 * <li>{@link org.apache.commons.beanutils.PropertyUtilsBean#setSimpleProperty(Object, String, Object)}</li>
 * </ul>
 * <li>{@link org.apache.commons.beanutils.BeanUtilsBean}</li>
 * <ul>
 * <li>{@link org.apache.commons.beanutils.BeanUtilsBean#copyProperty(Object, String, Object)}</li>
 * <li>{@link org.apache.commons.beanutils.BeanUtilsBean#setProperty(Object, String, Object)}</li>
 * </ul>
 * <li>{@link org.apache.commons.beanutils.locale.LocaleBeanUtilsBean}</li>
 * <ul>
 * <li>{@link org.apache.commons.beanutils.locale.LocaleBeanUtilsBean#setProperty(Object, String, Object, String)}</li>
 * </ul>
 * </ul>
 * 
 * @version $Revision: 555845 $ $Date: 2007-07-13 03:52:05 +0100 (Fri, 13 Jul 2007) $
 * @see org.apache.commons.beanutils.PropertyUtilsBean#setResolver(Resolver)
 * @since 1.8.0
 */
public interface Resolver {

    /**
     * Extract the index value from the property expression or -1.
     * 
     * @param expression
     *            The property expression
     * @return The index value or -1 if the property is not indexed
     * @throws IllegalArgumentException
     *             If the indexed property is illegally formed or has an invalid (non-numeric) value
     */
    int getIndex(String expression);

    /**
     * Extract the map key from the property expression or <code>null</code>.
     * 
     * @param expression
     *            The property expression
     * @return The index value
     * @throws IllegalArgumentException
     *             If the mapped property is illegally formed
     */
    String getKey(String expression);

    /**
     * Return the property name from the property expression.
     * 
     * @param expression
     *            The property expression
     * @return The property name
     */
    String getProperty(String expression);

    /**
     * Indicates whether or not the expression contains nested property expressions or not.
     * 
     * @param expression
     *            The property expression
     * @return The next property expression
     */
    boolean hasNested(String expression);

    /**
     * Indicate whether the expression is for an indexed property or not.
     * 
     * @param expression
     *            The property expression
     * @return <code>true</code> if the expresion is indexed, otherwise <code>false</code>
     */
    boolean isIndexed(String expression);

    /**
     * Indicate whether the expression is for a mapped property or not.
     * 
     * @param expression
     *            The property expression
     * @return <code>true</code> if the expresion is mapped, otherwise <code>false</code>
     */
    boolean isMapped(String expression);

    /**
     * Extract the next property expression from the current expression.
     * 
     * @param expression
     *            The property expression
     * @return The next property expression
     */
    String next(String expression);

    /**
     * Remove the last property expresson from the current expression.
     * 
     * @param expression
     *            The property expression
     * @return The new expression value, with first property expression removed - null if there are no more expressions
     */
    String remove(String expression);

}
